/Engine/Plugins/Media/ElectraCodecs/Source/ElectraDecoders/Public/IElectraDecoder.h
The return value indicates the following:
[EDecoderError](API\Plugins\ElectraDecoders\IElectraDecoder\EDecoderError) DecodeAccessUnit ( const [FInputAccessUnit](API\Plugins\ElectraDecoders\IElectraDecoder\FInputAccessUnit) & InInputAccessUnit, const [TMap](API\Runtime\Core\Containers\TMap)< [FString](API\Runtime\Core\Containers\FString), [FVariant](API\Runtime\Core\Misc\FVariant) > & InAdditionalOptions )